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Broadening of solar wind strahl pitch‐angles by the electron/electron instability: Particle‐in‐cell simulations
Author(s) -
Gary S. Peter,
Saito Shinji
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl030039
Subject(s) - pitch angle , physics , electron , solar wind , instability , computational physics , scattering , atomic physics , magnetic field , optics , geophysics , mechanics , quantum mechanics
Solar wind electrons in the suprathermal energy range from about 70 eV to greater than 1 keV usually are observed as two distinct, relatively tenuous components: an approximately isotropic halo and a strongly anisotropic “strahl” directed along the magnetic field. This manuscript describes a two‐dimensional electromagnetic particle‐in‐cell simulation in a magnetized, homogeneous, collisionless plasma with such a two‐component representation of suprathermal electrons. In this computation the electrostatic electron/electron instability is driven by a strahl with a large average speed along the background magnetic field B o . The simulation demonstrates that this instability leads to substantial strahl velocity scattering perpendicular to B o . The most important result here is that, for strahl speeds large compared to the halo thermal speed, after instability saturation the width of the electron pitch‐angle distribution exhibits a maximum as a function of electron energy.